1. Field of the Invention
The present invention relates to methods for manufacturing decorative workpieces such as decorative panels.
2. Description of the Related Art
Gravure, offset and flexography are being increasingly replaced for different applications by industrial inkjet printing systems, which have now proven their flexibility in use, such as variable data printing making short production runs and personalized products possible, and their enhanced reliability, allowing incorporation into production lines.
Inkjet technology, as digital printing technology has also caught the attention of manufacturers of decorative surfaces, such as laminate floor. In the current production process for manufacturing decorative panels as shown by FIG. 1, a paper manufacturer (11) supplies a paper roll (12) to a decor printer (13) who uses gravure printing (14) in order to deliver a decor paper roll (16) to a warehouse (17) of a floor laminate manufacturer (20). Some decor printers (13) are now investigating inkjet printing (15) instead of gravure printing. Rotogravure printing on the porous decor paper generally uses ink having a viscosity at 25° C. of 1 to 2 Pa·s, while the viscosity of inkjet inks is much lower, often about 1 to 15 mPa·s at 25° C. The floor laminate manufacturer (20) stores the decor paper rolls (16) having different decorative patterns in his warehouse (17). Depending on the market demand, the floor laminate manufacturer (20) then selects the decor rolls (16) with the desired decorative pattern in his warehouse (17). The selected decor rolls (16) are then impregnated (18) and cut to size (19) for manufacturing ready-to-use floor laminate (21). The warehouse (17) is necessary as a buffer for sudden large market demands of a specific floor laminate because there is a large time delay between ordering and delivering of new decorative paper rolls (16).
An approach to reduce the size of the warehouse and time delays is treated by EP 2431190 A (THEODOR HYMMEN), which discloses in FIG. 1 a method for producing a digitally printed sheet, web or plate-shaped workpiece (20) with wear-resistant surface including the steps of: A) providing a digital data set to a digital printing device (1); B) providing a printable workpiece (20) to the printing apparatus (1); C) digital printing at least an acrylate printing ink (22) on the printable workpiece (20) using the printing apparatus (1) and thereafter supplying a resin mixture (5, 21) to the digitally printed workpiece; and D) curing the resin mixture (5, 21) by means of a heated press (7). The time delay can be avoided by the floor laminate manufacturer incorporating the manufacturing of decorative paper rolls into its own production process.
Also aqueous inkjet inks have been used for manufacturing decorative laminates by single pass inkjet printing. For example, in the Palis roll-to-roll single pass printing systems (http://www.palis-digital.com/en/portfolio/sp-drucker.html) aqueous inkjet inks are printed on a paper substrate having a special ink acceptance layer.
An increase in waste of decorative workpieces has been observed on performing the digital printing of decorative patterns at the facilities of the laminate manufacturer. This increase of waste is observed not only in the more frequent short run productions, but especially when sizes of digital printed decorative patterns are different or when the shapes of digital printed decorative patterns are different. Therefore, there is a need to reduce the waste of decoration layer and workpieces.
DE102006057961 (BAUER JOERG) discloses a method of producing floor panels wherein an arrangement method is disclosed in FIG. 1 and described in [0027] but is silent about details in this arrangement method and the reasons behind this kind of arrangement.
EP2695746 (UNILIN BVBA), which became public available on 12 Feb. 2014, with a date of filing on 6 Aug. 2012, discloses a method wherein multiple rectangular-shaped decorative patterns are printed on a decoration layer but wherein the decorative patterns are arranged in predetermined areas based on the dimension of the predetermined areas. Therefore the dimensions of the decorative patterns are also fixed. But they are not a solution wherein multiple decorative patterns have to be arranged on a decoration layer and wherein the dimensions and shapes of the decorative patterns have a lot of variances.
DE102010036454 (FRITZ EGGER GMBH) discloses a similar method for arrangement of decorative patterns as in EP295746 (UNILIN BVBA) but also in here the decorative patterns are arranged in predetermined areas based on the dimension of the predetermined areas. Therefore the dimensions of the decorative patterns are also fixed. But they are not a solution wherein multiple decorative patterns have to be arranged on a decoration layer and wherein the dimensions and shapes of the decorative patterns have a lot of variances.